Manus Island's police chief has blasted the Abbott government's running of the immigration detention camp on the island, suggesting the recent fatal violence could have been avoided.

Police commander Alex N'Drasal said the protests were sparked by the failure to act on a list of grievances raised by the asylum seekers. He said the Australian government should improve the way the detention centre is run.

Meanwhile, the Australian government has suffered the ignominy of having its asylum-seeker policy publicly criticised by another foreign government - this time China, a country with its own chequered human rights record.

In a sign of lingering bilateral tension between Australia and its largest trading partner, China's Vice-Minister of Foreign Affairs, Li Baodong, said he was concerned about the "very important issue" of the treatment of refugees and asylum seekers, especially children, who arrive in Australia by boat.

"Indeed, we have proposed this question very candidly and also stated our concerns," Mr Li told reporters in Beijing. "We also asked if these refugees will be illegally repatriated to other countries."

Earlier on Thursday, Prime Minister Tony Abbott stood by Australia's tough offshore processing regime, insisting he would not give in to ''moral blackmail'' and expressing confidence in the facility.

''We will ensure that these camps are run fairly. They will be firm if necessary,'' Mr Abbott said.

But Greens leader Christine Milne on Friday called for a royal commission into the asylum seeker's death, saying she believed the Iranian man was ''murdered''.

''There is no way that an internal immigration department investigation is ever going to turn up what we need,'' Senator Milne told ABC radio. ''The gag orders are in place, people are afraid to speak out.''

She repeated her calls to shut down the offshore detention centres at Manus Island and Nauru.

''What we are seeing here is cruel and inhumane treatment of people. That is wrong and there is no excuse for it,'' Senator Milne said.

Monday night's violence - sparked after protesting asylum seekers apparently pushed down a fence and broke out of the centre - left one Iranian asylum seeker dead and scores injured.

Mr N'Drasal told Papua New Guinea newspaper The National: ''The Australian government should change its approach and act quickly on the petition which was handed to the authority last week by the transferees.''

He said the Australian government should hire detention centre staff with better experience, such as ''those who have worked in refugee camps''.

''These asylum seekers are educated people and should be treated like one,'' Mr N'Drasal said.

He confirmed to Fairfax Media that he had made the remarks but said he had been forbidden by his superiors in Port Moresby to say anything further on the issue.

His remarks came as Manus Island Member of Parliament Ron Knight said he believed that gun butts and batons had been used against rioting asylum seekers by the notorious ''mobile squad'', a paramilitary branch of the police who are the main law enforcers outside the camp.

Mr Knight said the blame for the violence lay primarily with the asylum seekers but said that their claims should be processed more quickly and the security infrastructure should be improved.

''I think it could have been handled a bit more diplomatically in the way they approach the asylum seekers and let them know information,'' he said.

Mr Knight backed the squad's use of force, saying it ''had to be brutal to be effective'' and adding that the present unit stationed there was professional and disciplined. A previous unit beat a local man to death last year.

Security continues to be bolstered on the island, with Mr Morrison confirming 50 more Wilson security staff were on standby on Thursday if violence again erupted.

Within a week the security firm G4S would be completely removed from the island as its contract would end, Immigration Minister Scott Morrison said.

On Wednesday, 51 Wilson security staff that are subcontracted to Transfield flew to the island. They joined 130 Wilson staff who were already stationed at the centre.

''In the 12 months we have been operating in Nauru not one person has come to any harm through our services,'' Transfield spokesman David Jamieson said. ''If there is any concern about taking over Manus, judge us by our actions.''

The concerns from China were raised in the context of a regular human rights dialogue, this year held in Beijing. But in previous iterations, both Chinese and Australian officials have usually responded to questions from reporters with general answers in order not to risk offence, keeping criticisms behind closed doors.

The leader of the Australian delegation, Gillian Bird, deputy secretary of the Department of Foreign Affairs and Trade, appeared to stick to the script. In a series of cautious answers, she said she was "very happy to respond on Australian policies and to explain and answer any questions".